Abstract

How traits influence species persistence is a fundamental question in ecology, evolution and palaeontology. We test the relationship between dietary traits and both species duration and locality coverage over 40 million years in North American canids, a clade with considerable ecomorphological disparity and a dense fossil record. Because ecomorphological generalization—broad resource use—may enable species to withstand disturbance, we predicted that canids of average size and mesocarnivory would exhibit longer durations and wider distributions than specialized larger or smaller species. Second, because locality coverage might reflect dispersal ability and/or survivability in a range of habitats, we predicted that high coverage would correspond with longer durations. We find a nonlinear relationship between species duration and degree of carnivory: species at either end of the carnivory spectrum tend to have shorter durations than mesocarnivores. Locality coverage shows no relationship with size, diet or duration. To test whether generalization (medium size, mesocarnivory) corresponds to an adaptive optimum, we fit trait evolution models to previously generated canid phylogenies. Our analyses identify no single optimum in size or diet. Instead, the primary model of size evolution is a classic Cope's Rule increase over time, while dietary evolution does not conform to a single model.

Highlights

  • The potential to predict emergent species- and community-level patterns and processes from functional traits is of great ecological2018 The Authors

  • The three dietary indices were preserved in 93 fossil canids of unknown diet, whose predicted principal component values are superimposed onto the extant plot

  • While most of the measures were standardized to account for body mass (e.g. RBL is a measure of the lower slicing blade divided by lower carnassial length, our proxy for mass), the morphological differences between hunters of small versus large prey remain in proportions of linear traits, such as relative jaw depth

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Summary

Introduction

The potential to predict emergent species- and community-level patterns and processes from functional traits is of great ecological2018 The Authors. Using geographical breadth and species longevity as measures of success, how do a species’ traits interact to make it successful over evolutionary time?. Abundance, range size and population size are measures of success that can be influenced by a variety of factors, such as body size [4,5], diet or prey choice [6], and dispersal ability [7]. Fossil ecosystems provide another dimension—time—and permit the analysis of taxon longevity in addition to geographical range as a metric of success. On an ecomorphological spectrum from generalization to specialization, small-bodied hypocarnivory and large-bodied bone-cracking hypercarnivory form opposite specialized extremes

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